U.S. patent application number 12/570403 was filed with the patent office on 2010-04-01 for medical manipulator.
This patent application is currently assigned to TERUMO KABUSHIKI KAISHA. Invention is credited to Ryohei KATSUKI, Hiroaki SANO.
Application Number | 20100079099 12/570403 |
Document ID | / |
Family ID | 42056697 |
Filed Date | 2010-04-01 |
United States Patent
Application |
20100079099 |
Kind Code |
A1 |
KATSUKI; Ryohei ; et
al. |
April 1, 2010 |
MEDICAL MANIPULATOR
Abstract
A medical manipulator includes an actuator block having a motor,
a coupler detachably mounted on the actuator block and having a
rotor connected to a rotatable shaft of the motor, a distal-end
working unit mounted on a distal end of a joint shaft, which
extends from the coupler and is operatively connected to the rotor
by a wire, an encoder for detecting an angular displacement of the
motor, and a controller for reading a signal from the encoder and
comparing the read signal with an operation command value for
energizing the motor through a feedback loop. The controller
outputs a signal having a level greater than the resolution of the
encoder and a lower operation limit of the motor within a range in
which the distal-end working unit remains still, and monitors the
angular displacement of the motor for thereby determining whether
the feedback loop is malfunctioning or not.
Inventors: |
KATSUKI; Ryohei;
(Fujinomiya-shi, JP) ; SANO; Hiroaki;
(Fujinomiya-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TERUMO KABUSHIKI KAISHA
Shibuya-ku
JP
|
Family ID: |
42056697 |
Appl. No.: |
12/570403 |
Filed: |
September 30, 2009 |
Current U.S.
Class: |
318/565 ;
318/568.24; 700/245 |
Current CPC
Class: |
A61B 34/71 20160201;
A61B 2090/067 20160201; G05B 23/0256 20130101; A61B 2017/0046
20130101; A61B 2034/742 20160201; A61B 2034/305 20160201; A61B
34/37 20160201; A61B 2017/00477 20130101; A61B 34/70 20160201 |
Class at
Publication: |
318/565 ;
700/245; 318/568.24 |
International
Class: |
G05B 23/02 20060101
G05B023/02; G06F 19/00 20060101 G06F019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2008 |
JP |
2008-256171 |
Claims
1. A medical manipulator comprising: an actuator block having a
motor including a rotatable shaft; a coupler detachably mounted on
the actuator block and having a rotor connected to the rotatable
shaft of the motor; a distal-end working unit mounted on a distal
end of a joint shaft, which extends from the coupler and is
operatively connected to the rotor by a power transmitting member;
an angle sensor for detecting an angular displacement of the motor;
and a controller for reading a signal from the angle sensor and
comparing the read signal with an operation command value for
energizing the motor through a feedback loop, wherein the
controller temporarily cuts off the feedback loop to turn the
feedback loop into an open loop, outputs a current signal to the
motor, and monitors the signal from the angle sensor within a range
in which the distal-end working unit remains still, for thereby
determining whether a system including the motor and the angle
sensor is malfunctioning or not.
2. A medical manipulator according to claim 1, wherein the actuator
block includes a speed reducer for reducing a speed of rotation of
the motor and transmitting the rotation of the motor at the reduced
speed to the rotor; and the controller determines whether the
system is malfunctioning or not within a range in which an output
shaft of the speed reducer remains still.
3. A medical manipulator according to claim 1, wherein the
controller outputs signals to the motor to rotate the rotational
shaft of the motor in respective normal and opposite
directions.
4. A medical manipulator according to claim 1, wherein the
controller determines whether the system is malfunctioning or not
when the medical manipulator is initialized after the feedback loop
is activated, and before the distal-end working unit is
operated.
5. A medical manipulator comprising: an actuator block having a
motor including a rotatable shaft; a coupler detachably mounted on
the actuator block and having a rotor connected to the rotatable
shaft of the motor; a distal-end working unit mounted on a distal
end of a joint shaft, which extends from the coupler and is
operatively connected to the rotor by a power transmitting member;
an angle sensor for detecting an angular displacement of the motor;
and a controller for reading a signal from the angle sensor and
comparing the read signal with an operation command value for
energizing the motor through a feedback loop, wherein the
controller monitors the signal from the angle sensor within a range
in which the distal-end working unit remains still, by outputting a
signal having a level greater than the resolution of the angle
sensor and a lower operation limit of the motor, for thereby
determining whether a feedback system including the motor and the
angle sensor is malfunctioning or not.
6. A medical manipulator comprising: an actuator block having a
motor including a rotatable shaft; a coupler detachably mounted on
the actuator block and having a rotor connected to the rotatable
shaft of the motor; a distal-end working unit mounted on a distal
end of a joint shaft, which extends from the coupler and is
operatively connected to the rotor by a power transmitting member;
an angle sensor for detecting an angular displacement of the motor;
a controller for reading a signal from the angle sensor and
comparing the read signal with an operation command value for
energizing the motor through a feedback loop; and a current sensor
for detecting a current value supplied to the motor and supplying
the detected current value to the controller, wherein the
controller inspects a system including the motor and the angle
sensor for malfunctioning, when the signal from the angle sensor
remains unchanged and the current value is equal to or greater than
a threshold value, depending on an operation at a given time.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from Patent Application No. 2008-256171 filed on Oct. 1,
2008, in the Japan Patent Office, of which the contents are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a medical manipulator for
actuating a distal-end working unit on the distal end of a joint
shaft with a motor that is energized by a controller, and more
particularly to a medical manipulator in which a motor for
actuating a distal-end working unit is feedback-controlled based on
a comparison of angular displacement of the motor and an operation
command value.
[0004] 2. Description of the Related Art
[0005] When performing an endoscopic surgery (also called
laparoscopic surgery), it is customary to form a plurality of
incisions in the body surface of the patient, insert trocars
(tubular instruments) into respective incisions as instrument
passage ports, and introduce distal ends of forceps having shafts
through the respective trocars into the body cavity to perform a
surgical operation on an affected part of the body. Working units
such as a gripper for gripping a living tissue, scissors, the blade
of an electric scalpel, etc., are mounted on distal ends of the
forceps.
[0006] An endoscopic surgical operation performed with forceps
requires the surgeon to be trained in advance, because the working
space in the body cavity is small and the forceps need to be
operated using the trocars as fulcrums. Since forceps that have
been used heretofore lack joints in the working unit on the distal
end thereof, such forceps have a small degree of freedom, and the
working unit can be operated only on an extension of the shaft.
Therefore, cases that can be handled under the usual training
practice for endoscopic surgery are limited to a certain range. The
surgeon needs to be trained and highly skilled in order to be able
to perform endoscopic surgery on various other cases not within
this limited range.
[0007] Attempts have heretofore been made to improve conventional
forceps and to develop a forceps having a plurality of joints in a
working unit thereof (see, for example, Japanese Laid-Open Patent
Publication No. 2004-105451). The manipulator disclosed in Japanese
Laid-Open Patent Publication No. 2004-105451 comprises a manually
operable operating unit, and a working unit replaceably mounted on
the operating unit. The disclosed manipulator is free of the
limitations and difficulties of conventional forceps, can be
operated easily to perform surgical techniques, and can be applied
to a wide variety of surgical cases. The manipulator can be used to
perform various surgical techniques by replacing the working unit
with working units of different types.
[0008] The manipulator includes a motor for moving the working
unit, and a controller for measuring the angular displacement of
the motor with an angle sensor, comparing a signal representative
of the measured angular displacement with an operation command
value, and controlling the motor through a negative feedback loop
based on the result of the comparison. The motor actuates a
distal-end working unit mounted on the distal end of a joint shaft
through a power transmitting member such as a wire.
[0009] A medical robot system has been proposed for actuating such
a manipulator via a robot arm (see, for example, U.S. Pat. No.
6,331,181).
[0010] In the manipulator described above, the controller compares
a signal representative of the measured angular displacement with
an operation command value, and controls the motor through a
negative feedback loop based on the result of the comparison. The
feedback control process makes it possible to operate the
distal-end working unit accurately according to the operation
command value.
[0011] However, if the feedback loop becomes accidentally broken in
some way, the feedback control process fails to operate normally.
Particularly, if a feedback route from the sensor to a subtracting
point is broken, then the feedback loop changes into an open loop,
and the controller fails to supply a feedback signal depending on
the operation command value, so that the distal-end working unit
could possibly operate unexpectedly.
[0012] Consequently, the signal line for transmitting the signal
from the angle sensor should desirably have a highly reliable
construction. The manipulator should also incorporate some means
therein for judging whether the feedback system is malfunctioning
or not, in preparation for unforeseeable situations. It is
desirable that the malfunction judgment be carried out without
adversely affecting the surgical operation being performed using
the manipulator.
SUMMARY OF THE INVENTION
[0013] It is an object of the present invention to provide a
medical manipulator, which is capable of judging whether a feedback
system is malfunctioning or not without adversely affecting a
surgical operation that is being performed using the
manipulator.
[0014] According to an aspect of the present invention, a medical
manipulator comprises an actuator block having a motor including a
rotatable shaft, a coupler detachably mounted on the actuator block
and having a rotor connected to the rotatable shaft of the motor, a
distal-end working unit mounted on a distal end of a joint shaft,
which extends from the coupler and is operatively connected to the
rotor by a power transmitting member, an angle sensor for detecting
an angular displacement of the motor, and a controller for reading
a signal from the angle sensor and comparing the read signal with
an operation command value for energizing the motor through a
feedback loop, wherein the controller temporarily cuts off the
feedback loop to turn the feedback loop into an open loop, outputs
a current signal to the motor, and monitors the signal from the
angle sensor within a range in which the distal-end working unit
remains still, for thereby determining whether a system including
the motor and the angle sensor is malfunctioning or not.
[0015] When the controller outputs a current signal to the motor
while the feedback loop is temporarily turned into an open loop,
and determines whether the system is malfunctioning or not within a
time range in which the distal-end working unit remains still, the
medical manipulator does not adversely affect the surgical
procedure presently being performed.
[0016] The actuator block may include a speed reducer for reducing
a speed of rotation of the motor and transmitting the rotation of
the motor at the reduced speed to the rotor, and the controller may
determine whether the system is malfunctioning or not within a
range in which an output shaft of the speed reducer remains still.
Since the output shaft of the speed reducer does not move even when
the coupler is removed from the actuator block, the operator of the
medical manipulator does not sense any visual oddness about the way
in which the medical manipulator operates.
[0017] The controller may output signals to the motor to rotate the
rotational shaft of the motor in respective normal and opposite
directions. Since the controller outputs signals to the motor to
rotate the rotational shaft thereof in respective normal and
opposite directions, even if the motor is less likely to rotate in
one of the directions due to gear backlash, the motor is more
likely to move in the opposite direction. Accordingly, the motor
and the angle sensor respond properly, and the feedback loop can be
checked for malfunctioning with increased reliability.
[0018] The controller may determine whether the system is
malfunctioning or not when the medical manipulator is initialized
after the feedback loop is activated, and before the distal-end
working unit is operated. Since the feedback loop is judged for
malfunctioning when the medical manipulator is initialized, the
medical manipulator will be operated with higher reliability during
the surgical procedure, in a subsequent operation mode of the
medical manipulator.
[0019] According to another aspect of the present invention, a
medical manipulator comprises an actuator block having a motor
including a rotatable shaft, a coupler detachably mounted on the
actuator block and having a rotor connected to the rotatable shaft
of the motor, a distal-end working unit mounted on a distal end of
a joint shaft, which extends from the coupler and is operatively
connected to the rotor by a power transmitting member, an angle
sensor for detecting an angular displacement of the motor, and a
controller for reading a signal from the angle sensor and comparing
the read signal with an operation command value for energizing the
motor through a feedback loop, wherein the controller monitors the
signal from the angle sensor within a range in which the distal-end
working unit remains still, by outputting a signal having a level
greater than the resolution of the angle sensor and a lower
operation limit of the motor, for thereby determining whether a
feedback system including the motor and the angle sensor is
malfunctioning or not.
[0020] When a signal whose level is greater than the resolution of
the angle sensor and a lower operation limit of the motor is output
to the motor within a range in which the distal-end working unit
remains still, only the signal from the angle sensor is changed
without moving the distal-end working unit. Consequently, it is
possible to determine whether the system is malfunctioning or not,
without adversely affecting the surgical procedure being
performed.
[0021] The above process of the controller can determine whether
the system is malfunctioning or not while the feedback loop remains
closed.
[0022] According to still another aspect of the present invention,
a medical manipulator comprises an actuator block having a motor
including a rotatable shaft, a coupler detachably mounted on the
actuator block and having a rotor connected to the rotatable shaft
of the motor, a distal-end working unit mounted on a distal end of
a joint shaft, which extends from the coupler and is operatively
connected to the rotor by a power transmitting member, an angle
sensor for detecting an angular displacement of the motor, a
controller for reading a signal from the angle sensor and comparing
the read signal with an operation command value for energizing the
motor through a feedback loop, and a current sensor for detecting a
current value supplied to the motor and supplying the detected
current value to the controller, wherein the controller inspects a
system including the motor and the angle sensor for malfunctioning,
when the signal from the angle sensor remains unchanged and the
current value is equal to or greater than a threshold value,
depending on an operation at a given time. The above process of the
controller can determine whether the system is malfunctioning or
not, even in an operation mode of the medical manipulator.
[0023] With the medical manipulator according to the present
invention, when the controller outputs a current signal to the
motor while the feedback loop is temporarily turned into an open
loop, and determines whether the system is malfunctioning or not
within a time range in which the distal-end working unit remains
still, the medical manipulator does not adversely affect the
surgical procedure being performed.
[0024] Furthermore, when a signal whose level is greater than the
resolution of the angle sensor and a lower operation limit of the
motor is output to the motor within a range in which the distal-end
working unit remains still, only the signal from the angle sensor
is changed without moving the distal-end working unit.
Consequently, it is possible to determine whether the system is
malfunctioning or not without adversely affecting the surgical
procedure being performed.
[0025] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings in which a preferred embodiment of the present invention
is shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a perspective view of a medical manipulator
according to an embodiment of the present invention;
[0027] FIG. 2 is a side elevational view of the medical
manipulator, with a working unit and an operating unit being
separated from each other;
[0028] FIG. 3 is a perspective view of the operating unit;
[0029] FIG. 4 is a perspective view of a distal-end working unit of
the medical manipulator;
[0030] FIG. 5 is a block diagram of a controller and the operating
unit, which are connected to each other by a cable;
[0031] FIG. 6 is a schematic view showing a system of the medical
manipulator for judging whether a feedback loop thereof is
malfunctioning or not;
[0032] FIG. 7 is a flowchart of a sequence for judging whether the
feedback loop is malfunctioning or not in a check mode after the
feedback loop has been activated, and for transitioning to an
operation mode following the check mode;
[0033] FIG. 8 is a flowchart of a sequence for judging whether the
feedback system is malfunctioning or not in the operation mode;
and
[0034] FIG. 9 is a schematic perspective view of a medical robot
system with the manipulator connected to the distal end of a robot
arm.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] A medical manipulator according to an embodiment of the
present invention will be described below with reference to FIGS. 1
to 9.
[0036] As shown in FIG. 1, a medical manipulator 10 according to an
embodiment of the present invention includes a distal-end working
unit 12 for gripping a portion of a living tissue, a curved needle,
or the like in order to carry out a certain surgical treatment. The
distal-end working unit 12 typically is referred to as a gripping
forceps, a needle driver (needle holder), or the like.
[0037] The manipulator 10 comprises an operating unit 14 on a
proximal end portion, which is held and operated by a human hand,
and a working unit 16 detachably mounted on the operating unit 14.
The operating unit 14 is electrically and detachably connected to a
controller 27 by a connector 24, thereby making up a manipulator
system.
[0038] The manipulator 10 basically includes the operating unit 14
and the working unit 16. The controller 27 for electrically
controlling the manipulator 10 is connected by the connector 24 to
a cable 62, which extends from the lower end of a grip handle 26 of
the operating unit 14. Some or all of the functions of the
controller 27 may be incorporated into the operating unit 14.
[0039] In the following description, the transverse directions in
FIG. 1 shall be referred to as X directions, vertical directions as
Y directions, and longitudinal directions of a hollow joint shaft
48 as Z directions. Among the X directions, the rightward direction
as viewed from the distal end is referred to as an X1 direction,
and the leftward direction as an X2 direction. Among the Y
directions, the upward direction is referred to as a Y1 direction,
and the downward direction as a Y2 direction. Among the Z
directions, the forward direction is referred to as a Z1 direction,
and the rearward direction as a Z2 direction. Unless otherwise
noted, these directions represent directions of the manipulator 10
when the manipulator 10 is in a reference attitude (i.e., neutral
attitude). The definitions of the above directions are for
illustrative purposes only, and the manipulator 10 can be used in
any of various orientations. For example, the manipulator 10 may be
used upside down.
[0040] The working unit 16 comprises a distal-end working unit 12
for performing a working operation, a coupler 15 connected to an
actuator block (actuator) 30 of the operating unit 14, and an
elongate hollow joint shaft 48 coupling the distal-end working unit
12 and the coupler 15 to each other. When a predetermined action is
performed on the actuator block 30, the working unit 16 can be
separated from the operating unit 14, so that the working unit 16
can be cleaned, sterilized, and serviced for maintenance. The
actuator block 30 refers to the block on which the working unit 16
is mounted, and is not limited to a structure housing motors (DC
motors) 40a, 40b, 40c therein. The actuator block 30 covers a joint
surface 30a (see FIG. 3) for connection to a bridge 28.
[0041] The distal-end working unit 12 and the joint shaft 48, which
are small in diameter, can be inserted into a body cavity 22
through a trocar 20 in the form of a hollow cylinder mounted in an
abdominal region or the like of the patient. The distal-end working
unit 12 is actuated by the operating unit 14 to perform various
surgical techniques, for example, to remove, grip, suture, or
ligate (tie-knot) an affected part of the patient's body inside the
body cavity 22.
[0042] The operating unit 14 includes a grip handle 26 that is
gripped by a human hand, the bridge 28 extending from an upper
portion of the grip handle 26, and an actuator block 30 connected
to a distal end of the bridge 28. As shown in FIG. 3, the grip
handle 26 extends in the Y2 direction from the end of the bridge
28, and has a length suitable for being gripped by a human hand.
The grip handle 26 has an input means for entering signals for
operating the distal-end working unit 12. The input means includes
a trigger lever 32 and a switch 36 disposed closely to the grip
handle 26 and projecting away from the grip handle 26 in the Z1
direction, and a composite input unit 34 and an operation switch
35, which face away from the grip handle 26 in the Y1
direction.
[0043] An LED 29 is mounted on the upper surface of the bridge 28
at a location which can easily be viewed by the operator of the
manipulator 10. The LED 29 is spaced from the operation switch 35
in the Z1 direction. The LED 29 serves as an indicator for
indicating a controlled state of the manipulator 10. The LED 29 is
large enough in size to be easily visually recognizable by the
operator, and yet is sufficiently small and light, so as not to
interfere with operations of the manipulator 10.
[0044] The cable 62 connected to the controller 27 has an end
connected to a lower end of the grip handle 26. The grip handle 26
and the cable 62 may be connected to each other by a connector.
[0045] The input means, which is incorporated into the operating
unit 14 for operating the distal-end working unit 12, will be
described below.
[0046] The operation switch 35 serves to selectively enable or
disable the manipulator 10. The LED 29 is located in a visually
recognizable position substantially centrally on the upper surface
of the bridge 28, in a juxtaposed relation to the operation switch
35. The LED 29 is turned on in synchronism with the operation
switch 35 when the operation switch 35 is turned on. Therefore,
when the operator turns on or off the operation switch 35, the
operator can reliably recognize and confirm turning on or turning
off of the operation switch 35 simply by visually checking the LED
29.
[0047] The controller 27 reads the state of the operation switch
35. When the operation switch 35 is turned on, the controller 27
sets the manipulator 10 in an operation mode. When the operation
switch 35 is turned off, the controller 27 sets the manipulator 10
in an automatic origin return mode, which returns the motors 40a,
40b, 40c to their origins. After the motors 40a, 40b, 40c have been
returned to their origins, the controller 27 sets the manipulator
10 in a stop mode. In the operation mode, the controller 27 enables
operation commands to be entered from the operating unit 14 to
energize the motors 40a, 40b, 40c. In the stop mode, the controller
27 deenergizes the motors 40a, 40b, 40c regardless of whether
operation commands are entered from the operating unit 14 or not.
The controller 27 distinguishes such modes, and switches between
different energized states of the LED 29 and other lamps based on
the distinguished modes.
[0048] The composite input unit 34 serves as a composite input
means for giving rotational commands, in rolling directions (shaft
rotating directions) and yawing directions (left and right
directions), to the distal-end working unit 12. The composite input
unit 34 includes, for example, a first input means, which operates
in shaft rotating directions for giving rotational commands in
rolling directions, and a second input means, which operates in
left and right directions for giving rotational commands in yawing
directions. The trigger lever 32 serves as an input means for
giving opening and closing commands to a gripper 60 (see FIGS. 1
and 4) of the distal-end working unit 12.
[0049] As shown in FIG. 2, the composite input unit 34 and the
trigger lever 32 are combined with input sensors 39a, 39b, 39c for
detecting movement strokes thereof. The input sensors 39a, 39b, 39c
supply detected stroke signals to the controller 27. Based on the
supplied stroke signals from the input sensors 39a, 39b, 39c, the
controller 27 energizes the motors 40a, 40b, 40c so as to rotate
pulleys 50a, 50b, 50c coupled respectively therewith, which in turn
actuate respective wires 54a, 54b, 54c (see FIG. 4) that operate
the distal-end working unit 12.
[0050] As shown in FIGS. 2 and 3, the trigger lever 32 is disposed
slightly below the bridge 28 and projects in the Z1 direction. The
trigger lever 32 is disposed in a position where it can easily be
operated by the index finger of the hand gripping the grip handle
26.
[0051] The trigger lever 32 is operatively connected to the grip
handle 26 by an arm 98, and is movable toward and away from the
grip handle 26. The arm 98 is connected to the input sensor 39c in
the grip handle 26. A distance that the trigger lever 32 has moved
toward or away from the grip handle 26 is detected by the input
sensor 39c, which supplies a signal representing the detected
distance to the controller 27. The trigger lever 32 can be pulled
by the finger toward the grip handle 26 in the Z2 direction, and
can be pushed away from the grip handle 26 by the finger in the Z1
direction. When the trigger lever 32 is thus pulled or pushed, the
controller 27 receives a signal from the input sensor 39c and
imparts opening and closing commands to the gripper 60.
[0052] The switch 36, which is spaced from the trigger lever 32 in
the Y2 direction, comprises an alternate switch. When the switch 36
is operated, the gripper 60 remains in a certain state (e.g., a
closed state), which is brought about by the trigger lever 32.
[0053] As shown in FIGS. 1 and 2, the coupler 15 of the working
unit 16 is covered with a resin cover 37. The coupler 15 houses the
pulleys 50a, 50b, 50c rotatably therein, which are connected to the
respective drive shafts of the motors 40a, 40b, 40c and are rotated
thereby. The motors 40a, 40b, 40c are combined with respective
speed reducers 42a, 42b, 42c, each in the form of a planetary gear
assembly, for example, having a speed reduction ratio ranging from
1:100 to 1:300.
[0054] The wires 54a, 54b, 54c (see FIG. 4) are trained
respectively around the pulleys 50a, 50b, 50c and extend through a
space in the joint shaft 48 to the distal-end working unit 12. The
wires 54a, 54b, 54c have portions fixed to the pulleys 50a, 50b,
50c (and also to pulleys 57a, 57b, 57c to be described later) so
that the wires 54a, 54b, 54c will not slip on the pulleys 50a, 50b,
50c. The wires 54a, 54b, 54c may be of the same type and have the
same diameter.
[0055] As shown in FIG. 4, the wires 54a, 54b, 54c, which extend
through the joint shaft 48, are trained respectively around
corresponding pulleys 57a, 57b, 57c disposed in the distal-end
working unit 12, which includes the gripper 60.
[0056] When the pulley 50a is rotated about its own axis by the
motor 40a, rotation of the pulley 50a is transmitted through the
wire 54a to the pulley 57a, thereby rotating the pulley 57a about
its own axis. Rotation of the pulley 57a is then transmitted to a
gear 55, a gear ring 64, and a gear 66, which selectively open and
close the gripper 60. The pulleys 50a, 50b, 50c, the wires 54a,
54b, 54c, and the pulleys 57a, 57b, 57c jointly make up a power
transmitting assembly, which operates mechanisms having three
degrees of freedom incorporated in the distal-end working unit 12,
for twisting the distal-end working unit 12 in rolling directions,
turning the distal-end working unit 12 horizontally in yawing
directions, and opening and closing the gripper 60. Since the
mechanisms having three degrees of freedom tend to interfere with
each other, the motors 40a, 40b, 40c are energized to operate the
mechanisms so as not to interfere with each other.
[0057] The coupler 15 has two engaging teeth 200 disposed
respectively on opposite side surfaces thereof, and three fitting
holes 202a, 202b, 202c formed therein, which open on a lower
surface thereof. The three fitting holes 202a, 202b, 202c are
disposed near ends of the coupler 15 in the Z1 and Z2 directions,
and extend in the Y directions.
[0058] The actuator block 30 houses therein three motors 40a, 40b,
40c, which extend in parallel to each other, and are arrayed at
spaced intervals along the Z directions in association with the
respective mechanisms having three degrees of freedom in the
distal-end working unit 12. The motors 40a, 40b, 40c are small in
size and diameter. The actuator block 30 that houses the motors
40a, 40b, 40c has a flat compact shape. The actuator block 30 is
disposed downwardly of the end of the operating unit 14 in the Z1
direction. The motors 40a, 40b, 40c are energized under the control
of the controller 27, based on actions made by the operator on the
operating unit 14.
[0059] The motors 40a, 40b, 40c also are combined with respective
rotary encoders (or angle sensors, hereinafter referred to as
"encoders") 44a, 44b, 44c for detecting angular displacements of
the respective motor drive shafts. The rotary encoders 44a, 44b,
44c supply detected angle signals to the controller 27.
[0060] Angular displacements detected by the encoders 44a, 44b, 44c
are referred to for causing the three-axis mechanisms of the
distal-end working unit 12 to reach desired angles. In order to
detect the attitude of the distal-end working unit 12 accurately,
the encoders 44a, 44b, 44c may be incorporated into the distal-end
working unit 12, for directly detecting angular displacements of
the three-axis mechanisms of the distal-end working unit 12
accurately. However, for reasons 1) to 7) to be described in detail
below, the encoders 44a, 44b, 44c detect the angular displacements
of the motors 40a, 40b, 40c in order to indirectly detect the
angular displacements of the three-axis mechanisms.
[0061] 1) Since the distal-end working unit 12 is small and the
space therein is highly limited, it is difficult to incorporate
sensors in the distal-end working unit 12. 2) Even if sensors could
be incorporated in the distal-end working unit 12, the weight of
the manipulator including the distal-end working unit 12 with such
sensors incorporated therein would be heavy at the distal end and
could not easily be operated. 3) Since the working unit 16 is
detachably mounted on the operating unit 14, electric connectors
would be needed to provide electric connections for any sensors
incorporated in the distal-end working unit 12. 4) The working unit
16 should desirably be free of electric components and electric
contact points, because the working unit 16 periodically needs to
be cleaned. 5) Depending on the type of working unit 16, high
voltage may be applied to the working unit for burning living
tissue being treated by the working unit 16, in which case it is
difficult to electrically insulate sensors incorporated within the
distal-end working unit 12. 6) Since the working unit 16 is
expendable, the working unit 16 preferably should be inexpensive.
7) Since the distal-end working unit 12 includes rotatable shafts,
and since movable wires 54a, 54b, 54c extend through the joint
shaft 48, leads connected to sensors incorporated in the distal-end
working unit 12 may become broken, leading to damage to the
feedback system including the sensors.
[0062] With respect to the above reason 7), inasmuch as the medical
manipulator 10 is required to be highly reliable, a negative
feedback loop 508 (see FIG. 6) for actuating the distal-end working
unit 12 desirably should be constructed from as few units as
possible. With the medical manipulator 10, the feedback loop 508
comprises only the operating unit 14, the cable 62, and the
controller 27, and hence the medical manipulator 10 is highly
reliable.
[0063] As shown in FIG. 2, the pulleys 50a, 50b, 50c in the coupler
15 have respective criss-cross coupling teeth 51a, 51b, 51c on
lower ends thereof in the Y2 direction, and the rotatable shafts of
the motors 40a, 40b, 40c in the actuator block 30 have respective
criss-cross coupling recesses 41a, 41b, 41c. The coupling teeth
51a, 51b, 51c can engage in the respective coupling recesses 41a,
41b, 41c. When the coupler 15 is mounted on the actuator block 30,
the coupling teeth 51a, 51b, 51c engage in the respective coupling
recesses 41a, 41b, 41c in order to transmit the rotation of the
motors 40a, 40b, 40c to the pulleys 50a, 50b, 50c. The coupling
teeth 51a, 51b, 51c and the coupling recesses 41a, 41b, 41c may
have shapes other than criss-cross shapes.
[0064] An ID unit 104, which carries an ID (identification) mark
for identifying the individual working unit 16, is disposed on the
coupler 15.
[0065] The ID mark carried by the ID unit 104 comprises a QR code
in the form of a two-dimensional bar code for identifying the
working unit 16. The QR code is peculiar to a single working unit
16, and hence different QR codes are assigned respectively to
different working units 16. The QR code contains various pieces of
information including the type, specifications, serial number,
production factory, production date, tradename, etc., of the
working unit 16.
[0066] The operating unit 14 includes a camera 106 for reading the
QR code of the ID unit 104 of the connected working unit 16, and
for supplying the read QR code to the controller 27. The camera 106
is disposed in a position facing the ID unit 104. The operating
unit 14 also includes two LEDs 105, which are positioned one on
each side of the camera 106, for illuminating the ID unit 104 of
the connected working unit 16. The camera 106 may be replaced with
a bar-code reader or a bar-code scanner for reading the ID mark of
the ID unit 104.
[0067] In order to remove the coupler 15 from the operating unit
14, the operator simultaneously presses levers 206 disposed on
respective opposite sides of the actuator block 30, thereby tilting
the levers 206 outwardly to bring tapered wedges 206a of the levers
206 out of engagement with respect to engaging teeth 200 disposed
on respective opposite sides of the coupler 15. Thereafter, the
coupler 15 can be pulled and removed from the operating unit 14
upwardly in the Y1 direction. The actuator block 30 has three
alignment pins 212a, 212b, 212c on an upper surface thereof. The
alignment pins 212a, 212b, 212c can be fitted respectively into
fitting holes 202a, 202b, 202c formed in the coupler 15, for
thereby stably holding the coupler 15 on the actuator block 30. In
order to connect the coupler 15 to the operating unit 14, the
operator aligns the alignment pins 212a, 212b, 212c respectively
with the fitting holes 202a, 202b, 202c, and inserts the alignment
pins 212a, 212b, 212c respectively into the fitting holes 202a,
202b, 202c by lowering the coupler 15 in the Y2 direction. The
levers 206 are displaced outwardly while sliding over the outer
surfaces of the engaging teeth 200. Then, the levers 206 snap back
under the resiliency of the resilient members, thus bringing the
wedges 206a into engagement with the engaging teeth 200, whereby
the coupler 15 becomes mounted completely on the actuator block
30.
[0068] A working unit detecting means 107 for detecting whether the
coupler 15 has been placed on the actuator block 30 or not is
disposed on an upper surface 30b of the actuator block 30 at one
end thereof in the Z2 direction. The working unit detecting means
107 is in the form of a photointerruptor comprising an LED 107a as
a light emitter and a photodiode 107b as a light detector, which
are positioned in confronting relation to each other. When a light
shield 109 (see FIG. 2) on the rear end of the coupler 15 is
inserted between the LED 107a and the photodiode 107b, the light
shield 109 blocks light emitted from the LED 107a toward the
photodiode 107b, thereby detecting that the coupler 15 is mounted
on the actuator block 30. The LED 107a and the photodiode 107b
confront each other in the X directions, and are disposed closely
to each other.
[0069] The actuator block 30 includes a pair of independent
engaging fingers 210 for holding the coupler 15 of the working unit
16 and the three alignment pins 212a, 212b, 212c for positioning
and holding the coupler 15.
[0070] The two engaging fingers 210 are pivotally mounted in
symmetrical positions on respective outer side surfaces thereof,
which face in the X1 and X2 directions. The engaging fingers 210
comprise respective pusher surfaces 204 and respective levers 206,
which extend in the Y1 direction from the pusher surfaces 204. The
levers 206 project slightly from the upper surface of the actuator
block 30 in the Y1 direction, and have respective tapered wedges
206a on upper inner surfaces thereof for engaging with the
respective engaging teeth 200 on outer side surfaces of the coupler
15 when the coupler 15 is mounted on the actuator block 30. The
engaging fingers 210 are normally biased by resilient members, not
shown, to displace the levers 206 inwardly toward each other.
[0071] The alignment pins 212a, 212b, 212c are disposed for
alignment with the respective fitting holes 202a, 202b, 202c. Among
the three alignment pins 212a, 212b, 212c, two of the alignment
pins 212a, 212b are disposed near the end of the upper surface of
the actuator block 30 in the Z1 direction, whereas the other
alignment pin 212c is disposed near the other end of the upper
surface of the actuator block 30 in the Z2 direction. The alignment
pins 212a, 212b, 212c extend in the Y1 direction. Alignment pins
212a and 212b, which are disposed near the end of the upper surface
of the actuator block 30 in the Z1 direction, are spaced from each
other in the X directions.
[0072] Since the actuator block 30 has three alignment pins 212a,
212b, 212c, the coupler 15 is supported by the actuator block 30 at
three positions corresponding to the alignment pins 212a, 212b,
212c, whereby the coupler 15 is simply and reliably positioned with
respect to the actuator block 30. Since the three alignment pins
212a, 212b, 212c are not positioned in a linear manner, but rather
in a triangular pattern, the alignment pins 212a, 212b, 212c can
hold the coupler 15 stably against twisting forces applied in any
direction. At least two of the alignment pins 212a, 212b, 212c may
be effective to reliably position and hold the coupler 15 stably on
the actuator block 30. If two such alignment pins are spaced from
each other in the Z directions, then the alignment pins are
effective to hold the coupler 15 more stably on the actuator block
30.
[0073] A communication system 700 involving the controller 27 and
the operating unit 14 will be described below with reference to
FIG. 5.
[0074] The communication system 700 comprises the controller 27,
the operating unit 14, the connector 24, and the cable 62.
[0075] The controller 27 includes a CPU 600 connected to an FPGA
(Field Programmable Gate Array) 602 and a motor driver 606. The
FPGA 602 comprises an interface 604 and a counter 603.
[0076] The operating unit 14 includes an A/D converter (ADC)
618.
[0077] The communication system 700 also transmits signals to and
from the camera 106, the LED 29, the LED 107a, the switch 36, and
the photodiode 107b, which are omitted from illustration in FIG. 5.
Since the signals from the camera 106 represent a large amount of
image information, such signals may be transmitted by an
independent signal transmitting means if necessary.
[0078] Power lines 740, 741, 742, each comprising two leads, which
are connected respectively to the motors 40a, 40b, 40c, extend
through the cable 62 to the motor driver 606 of the controller 27.
Signal lines 743, 744, 745, each of which comprises two leads for
sending respective phase output pulse signals, i.e., A-phase and
B-phase signals that are 90.degree. out of phase with each other,
are connected respectively to the encoders 44a, 44b, 44c, and
extend through the cable 62 to the counter 603. The counter 603
counts pulses based on the A-phase and B-phase signals from the
encoders 44a, 44b, 44c, determines the angular displacements of the
motors 40a, 40b, 40c, and supplies the determined angular
displacements to the CPU 600. Analog signals output from the input
sensors 39a, 39b, 39c are supplied through the A/D converter 618 to
the interface 604.
[0079] The output signals from the encoders 44a, 44b, 44c may be
multiplied by a multiplier for increasing detection accuracy,
sometime before the output signals are supplied to the counter 603,
or processed and supplied as angular displacement signals to the
CPU 600. The communication system 700 has a communication rate,
which is high enough so as not to adversely affect the feedback
control process performed through the feedback loop 508 (see FIG.
6).
[0080] A system of the medical manipulator 10 for judging whether
the feedback loop 508 is malfunctioning or not will be described
below with reference to FIG. 6. Although the distal-end working
unit 12 of the medical manipulator 10 includes mechanisms having
three degrees of freedom, the system shown in FIG. 6 schematically
illustrates only the mechanism thereof involving the yaw axis.
[0081] As shown in FIG. 6, the controller 27 comprises an operation
command value setting unit 500 for determining a target angular
displacement in the yawing direction based on a signal obtained
from the composite input unit 34 and outputting the determined
target angular displacement as an operation command value C, a
subtracting point 502 for determining the error or difference E
between the angular displacement F of the motor 40b supplied from
the counter 603 and the operation command value C, a compensator
504 for compensating for the error .epsilon., and a malfunction
decision unit 506 for determining whether the feedback loop 508 is
malfunctioning or not based on the operation command value C and
the angular displacement F. The controller 27 also includes an
opener for temporarily cutting off the path between the counter 603
and the subtracting point 502 to thereby turn the feedback loop 508
into an open loop, and an input switcher 510 for selecting either
one of the operation command value setting unit 500 and the
malfunction decision unit 506 as an input source thereof. The input
switcher 510 has an output terminal connected to a current sensor
505, which comprises a Hall device, for example. The opener and the
input switcher 510 are operated by the malfunction decision unit
506. When the medical manipulator 10 is in a normal operation mode,
the opener connects the path between the counter 603 and the
subtracting point 502, thereby closing the feedback loop 508, and
the input switcher 510 selects the operation command value setting
unit 500 as its input source.
[0082] The operation command value setting unit 500 integrates
positive and negative signals obtained from the composite input
unit 34 into the operation command value C. The operation command
value setting unit 500 may set an appropriate dead zone for the
positive and negative signals obtained from the composite input
unit 34, so that the operation command value C will not fluctuate
when the medical manipulator 10 is not in operation. The
compensator 504 serves as a control means for compensating for the
error .epsilon. to converge to zero (0) quickly and stably. The
compensator 504 performs a PID compensating process, for
example.
[0083] When the medical manipulator 10 is in a check mode, at a
time when the medical manipulator 10 is initialized but before the
distal-end working unit 12 is operated, the malfunction decision
unit 506 controls the opener to cut off the path between the
counter 603 and the subtracting point 502 to thereby turn the
feedback loop 508 into an open loop, and also controls the input
switcher 510 to select the malfunction decision unit 506 as its
input source. In the check mode, the malfunction decision unit 506
supplies small inspection signals .+-.A to the input switcher 510
and monitors the angular displacement F of the motor 40b supplied
from the counter 603 to determine whether the feedback loop 508,
which includes the motor 40b and the encoder 44b, is malfunctioning
or not.
[0084] The malfunction decision unit 506 can also determine whether
the feedback loop 508 is malfunctioning or not in a composite
fashion, based on a current value I detected by the current sensor
505.
[0085] When the malfunction decision unit 506 detects a
malfunction, the controller 27 displays a malfunction indication
and deenergizes the motor driver 606. Some or all of the functions
of the controller 27 shown in FIG. 6 may be implemented by
software.
[0086] The angular displacement F of the motor 40b is produced when
the A-phase and B-phase signals output from the encoder 44b are
supplied to the counter 603, and pulses of the A-phase and B-phase
signals are counted by the counter 603. The error .epsilon.
produced by the subtracting point 502 is compensated for by the
compensator 504. The motor driver 606 outputs a current to energize
the motor 40b, which in turn rotates the drive shaft of the motor
40b. The rotational speed of the drive shaft of the motor 40b is
reduced by the speed reducer 42b, which transmits a reduced-speed
rotation from the output shaft thereof to the pulley 50b. The
pulley 50b moves the wire 54b to rotate the pulley 57b, which
operates the distal-end working unit 12 in the yawing directions.
While the distal-end working unit 12 is in operation, the encoder
44b outputs A-phase and B-phase signals depending on the direction
and the amount by which the motor 40b has rotated. The counter 603
counts the pulses of the A-phase and B-phase signals, and outputs
the angular displacement F of the motor 40b. When the distal-end
working unit 12 reaches the target angular displacement, the
operation command value C and the angular displacement F are equal
to each other, while the error .epsilon. is represented by
.epsilon.=C-F=0. Therefore, the current output from the motor
driver 606 becomes nil, thus stopping the motor 40b, the pulley
50b, and the pulley 57b. The negative feedback loop 508 is made up
collectively by the motor 40b which serves as an actuator, the
encoder 44b acting as a sensor, and the subtracting point 502,
etc., of the medical manipulator 10.
[0087] Sequences for detecting malfunction of the feedback loop 508
of the medical manipulator 10 will be described below. The
malfunction detecting sequences include a sequence performed in the
check mode at a time when the medical manipulator 10 is initialized
after the feedback loop 108 has been activated but before the
distal-end working unit 12 is operated, and a sequence performed in
the operation mode, in which inputs from the composite input unit
34 and the trigger lever 32 are validated while the distal-end
working unit 12 is in operation.
[0088] First, the sequence for detecting a malfunction of the
feedback loop 508 in the check mode after the feedback loop 108 has
been activated will be described below with reference to FIG. 7.
The check mode shown in FIG. 7 is carried out immediately after the
feedback loop 108 has been activated.
[0089] In step S1, the medical manipulator 10 is initialized.
Specifically, the count value of the counter 603 and the operation
command value C are preset to zero (0), and any inputs from the
composite input unit 34 and the trigger lever 32 are temporarily
made invalid. It is confirmed that the angular displacement F
obtained through the communication system 700 is nil. At this time,
it is assumed that the working unit 16 is mounted on the operating
unit 14.
[0090] In step S2, the opener cuts off the path between the counter
603 and the subtracting point 502 to thereby turn the feedback loop
508 into an open loop, and the input switcher 510 selects the
malfunction decision unit 506 as its input source. The malfunction
decision unit 506 supplies a small inspection signal A to the input
switcher 510 and monitors the angular displacement F of the motor
40b, which is output from the counter 603. At this time, the
malfunction decision unit 506 may refer to the current sensor 505
in order to check if a current I depending on the inspection signal
A is generated normally or not, and may provide a suitable current
feedback.
[0091] The inspection signal A is a small signal, and the motor
torque produced by the current I depending on the inspection signal
A is small, so that the current I essentially will not actuate the
speed reducer 42b or the distal-end working unit 12. However, the
produced motor torque can actuate the speed reducer 42b and the
distal-end working unit 12 within a certain non-load range, which
is commensurate with the play and backlash of the gears of the
speed reducer 42b and the distal-end working unit 12. Although the
non-load range is considerably small, it can be detected by the
encoder 44b. At this time, movement of the distal-end working unit
12 cannot be confirmed at least with normal perception, and such
movement does not make the operator feel visually odd about the way
in which the medical manipulator 10 operates. The inspection signal
.+-.A can be determined by computation, simulation,
experimentation, or the like.
[0092] If the feedback loop 508 is not malfunctioning, then the
motor 40b rotates within the non-load range, and the rotation of
the motor 40b is detected by the encoder 44b. Thus, the operator
can recognize that the feedback loop 508 is operating normally.
[0093] If a drive line of the feedback loop 508, i.e., the power
line 741, is suffering from a malfunction such as a disconnection,
short circuit, or the like, then the motor 40b is not rotated, or
is rotated only slightly. If a feedback line of the feedback loop
508, i.e., the encoder 44b, the counter 603, the communication
system 700, and interconnections therebetween, is suffering from a
malfunction, then no rotation of the motor 40b is detected, and the
angular displacement F supplied to the subtracting point 502
remains nil. Irrespective of whether the drive line or the feedback
line of the feedback loop 508 is suffering from a malfunction,
therefore, the angular displacement F remains unchanged.
[0094] In step S3, a change AF in the angular displacement F and a
threshold value T1 are compared with each other to confirm that
.DELTA.F>T1. The threshold value T1 is a small value for
excluding measurement errors. If .DELTA.F=T1, i.e., if the angular
displacement F undergoes no substantial change, then the motor 40b
may not be rotating due to a malfunction of the drive system for
the motor 40b, e.g., the motor driver 606. Control then goes to
step S4 for a more detailed check. If .DELTA.F>T1, then since
the feedback loop 508 is functioning normally, the input switcher
510 selects the operation command value setting unit 500 as its
input source, and the feedback loop 508 is closed in step S6. At
this time, the check mode shown in FIG. 7 is finished. Then,
control proceeds to the operation mode shown in FIG. 8.
[0095] There are possibly three cases which can lead to .DELTA.F
being less than or equal to T1 (.DELTA.F=T1). The first case is
when no current is supplied from the power line 741 and the motor
40b is not energized. The second case occurs when, although the
motor 40b is energized, the feedback line of the feedback loop 508
suffers from a malfunction and the angular displacement F of the
motor 40b is not detected. The third case occurs when, although the
feedback loop 508 is normal, the motor 40b is less likely to move
in a normal direction depending on the polarity of the gear
backlash. In the third case, the motor 40b is more likely to move
in an opposite direction, but is mechanically less likely to move
in a normal direction. Since the inspection signal A is small, the
torque generated by the motor 40b is not large enough in the third
case. In the third case, the motor 40b will still be properly
energized in a subsequent operation mode.
[0096] In step S4, the inspection signal A is changed to an
inspection signal -A.
[0097] In step S5, the change .DELTA.F in the angular displacement
F and the threshold value T1 are compared with each other to
confirm that .DELTA.F<-T1. If .DELTA.F=-T1, then it is judged
that the feedback loop 508 is suffering from a malfunction. If
.DELTA.F<-T1, then the feedback loop 508 is operating normally.
This corresponds to the third case, in which the motor 40b is
mechanically less likely to move in a normal direction due to gear
backlash, but is more likely to move in the opposite direction. The
feedback loop 508 is judged at least to be electrically normal.
Control then proceeds to step S6, whereupon the check mode is
finished.
[0098] If .DELTA.F=-T1, then it is judged that the feedback loop
508 is suffering from a malfunction in the first case or the second
case. Control then proceeds to step S7 to carry out a malfunction
handling process. In the malfunction handling process, the current
I is brought back to zero (0), a predetermined malfunction alarm is
generated, and the motor driver 606 is deenergized.
[0099] According to the sequence for determining whether the
feedback loop 508 is malfunctioning or not, in the check mode, as
described above, the feedback loop 508 is temporarily changed into
an open loop, and the inspection signal .+-.A is output to the
motor 40b to cause the motor 40b to produce a torque, which is
small enough to keep the distal-end working unit 12 from moving.
The motor 40b is then rotated in a non-load range because of gear
backlash, and the signal from the encoder 44b is changed without
moving the distal-end working unit 12. Therefore, the operator is
able to judge whether a malfunction in the feedback loop 508 has
occurred, without sensing any visual oddness about the way in which
the medical manipulator 10 operates. Since the feedback loop 508
includes the communication system 700, the communicating function
of the communication system 700 also is checked.
[0100] Furthermore, inasmuch as the motor 40b is energized only to
an extent in which the distal-end working unit 12 is not moved, the
feedback loop 508 can be checked for malfunctioning, even when the
distal-end working unit 12 has reached the end of its operating
range, e.g., when the gripper 60 is closed.
[0101] Moreover, the motor 40b is energized by the inspection
signals .+-.A for rotation in both normal and opposite directions.
Therefore, even if the motor 40b is less likely to rotate in one of
the directions due to gear backlash, the motor 40b is more likely
to rotate in the other direction. Consequently, the motor 40b and
the encoder 44b respond properly, and the feedback loop 508 can be
checked for malfunctioning with increased reliability.
[0102] Since the feedback loop 508 is judged for malfunctioning in
the check mode when the medical manipulator 10 is initialized, the
medical manipulator 10 can be operated with higher reliability when
a surgical procedure is carried out in a subsequent operation
mode.
[0103] The encoder 44b is used as an angle sensor, and outputs
A-phase and B-phase pulse signals. Since the controller 27 checks
the feedback loop 508 based on the count value of the counter 603,
which counts the pulses of the A-phase and B-phase pulse signals,
the controller 27 can simply and reliably determine whether the
feedback loop 508 is malfunctioning or not.
[0104] Since the current I corresponding to the inspection signals
.+-.A is small, no wasteful energy will be consumed for energizing
the motor 40b.
[0105] Although, in the sequence shown in FIG. 7, it has been
assumed that the working unit 16 is mounted on the operating unit
14, the working unit 16 may not actually be mounted on the
operating unit 14 in all cases. If the working unit 16 is not
mounted on the operating unit 14, then the inspection signals .+-.A
may be of a magnitude so as to energize the motor 40b in a non-load
range, corresponding to the backlash of the gears of the speed
reducer 42b. Assuming that the inspection signals .+-.A have such a
magnitude, even when the coupler 15 is removed from the actuator
block 30, the operator does not experience any sense of visual
oddness, because the exposed output shaft of the speed reducer 42b
does not move.
[0106] While the feedback loop 508 remains closed, a positional
signal, whose level is greater than the resolution of the encoder
44b and the lower operation limit of the motor 40b, but whose level
is not strong enough to move the distal-end working unit 12, may be
output as an operation command value C to the motor 40b. The signal
from the encoder 44b may be monitored to determine whether the
feedback loop 508 is malfunctioning or not. According to this
alternative process, it is possible to determine whether the
feedback loop 508 is malfunctioning or not while the feedback loop
508 remains closed.
[0107] In step S8, the controller 27 confirms the signal from the
working unit detecting means 107, and waits until the working unit
16 is mounted on the operating unit 14. Once the controller 27
confirms that the working unit 16 has been mounted on the operating
unit 14, control proceeds to step S9.
[0108] In step S9, the camera 106 captures an image of the ID unit
104, and the controller 27 acquires the type, individual number,
etc., of the working unit 16.
[0109] In step S10, the controller 27 performs a type-specific
initializing process based on the type of working unit 16.
[0110] In step S11, the controller 27 validates inputs from the
composite input unit 34 and the trigger lever 32, and also
validates the operation command value setting unit 500, thereby
allowing the distal-end working unit 12 to operate based on actions
of the operator. Thereafter, the operation command value setting
unit 500 outputs an operation command value C to actuate the
distal-end working unit 12, in all but certain exceptional
processing modes including a stop mode, an origin return mode,
etc.
[0111] The sequence for detecting a malfunction of the feedback
loop 508 in the operation mode will be described below with
reference to FIG. 8. The sequence shown in FIG. 8 is carried out at
given small time intervals during the operation mode.
[0112] In step S101 shown in FIG. 8, the malfunction decision unit
506 refers to the angular displacement F in order to determine
whether each of the axes of the distal-end working unit 12 is in
operation or not. Basically, the malfunction decision unit 506
waits, even if only one of the three axes of the distal-end working
unit 12 is in operation. However, the malfunction decision unit 506
may still perform the determining sequence, described below, even
if one of the three axes of the distal-end working unit 12 is
stopped.
[0113] In step S102, the malfunction decision unit 506 refers to
the current sensor 505, to check the current I for the stopped
axis.
[0114] In step S103, the malfunction decision unit 506 determines
the operating state of the stopped axis, according to a given
operating state determining process. The operating state
determining process determines the operating state of the gripper
60, for example, as one of four operating states, i.e., an
operating state in which the gripper 60 is stopped under no load,
an operating state in which the gripper 60 is gripping a workpiece,
e.g., a needle, an operating state during which the gripper 60 is
being opened, and an operating state during which the gripper 60 is
being closed. The gripper 60, which is stopped while being opened
and closed in the latter two operating states, may possibly be
malfunctioning. The gripper 60, which is stopped while gripping a
workpiece in the former two operating states, may also possibly be
malfunctioning depending on the current I that is output from the
motor driver 606.
[0115] In step S104, the malfunction decision unit 506 reads a
current threshold value It, which is set for each of the operating
states determined in step S103, from a given memory for each
stopped axis.
[0116] In step S105, the malfunction decision unit 506 compares the
current I with the current threshold value It. If I>It, then
control goes to step S106. If I=It, then the present cycle of the
sequence is ended.
[0117] In step S106, the malfunction decision unit 506 checks the
feedback loop 508 for malfunctioning, since the feedback loop 508
is highly likely to be malfunctioning because the current I, which
is greater than the current threshold value It, is flowing through
the stopped axis. Specifically, when the flowing current I is
greater than the current threshold value It, the motor
corresponding to the stopped axis is considered to be generating a
torque. However, since the angular displacement F is not changed,
the mechanical components involved may be mechanically stopped, or
the feedback loop 508 including the corresponding encoder, the
counter 603, etc., may be malfunctioning. Therefore, an inspecting
process, which is the same as steps S2 to S7 shown in FIG. 6, is
carried out in order to inspect the feedback loop 508. When the
gripper 60 is gripping the workpiece while it is stopped, a
considerably large current is supplied to the motor to generate the
gripping force. Therefore, the current threshold value is read for
each axis and for each operating state.
[0118] According to the sequence shown in FIG. 8, when the
distal-end working unit 12 is stopped, i.e., when the angular
displacement F is not changed, and also when the current I that is
flowing is equal to or greater than the current threshold value It
depending on the operation being conducted at that time, the
feedback loop 508 is inspected for malfunctioning. Therefore, the
feedback loop 508 can be determined for malfunctioning in the
normal operation mode, whereby reliability of the medical
manipulator 10 is increased.
[0119] The system shown in FIG. 6, and the sequences shown in FIGS.
7 and 8, schematically illustrate only the mechanism involving the
yaw axis. However, feedback loops for controlling other mechanisms
involving the roll axis and the gripper 60 can similarly be
provided to determine whether such mechanisms are malfunctioning or
not, in the same manner as described above. The feedback loops for
controlling mechanisms involving the yaw axis and the roll axis and
the gripper 60 may simultaneously be provided to determine whether
these mechanisms are malfunctioning. When a malfunction in any of
the feedback loops for controlling mechanisms involving the yaw
axis, the roll axis and the gripper 60 is detected, a warning may
be issued in order for the operator to recognize which feedback
loop is malfunctioning.
[0120] The medical manipulator 10 may be applied to a medical robot
system 800 as shown in FIG. 9, for example.
[0121] The medical robot system 800 has an articulated robot arm
802 and a console 804, with a working unit 806 connected to a
distal end of the robot arm 802. The distal end of the robot arm
802 incorporates therein a manipulator 808, which includes the same
mechanisms as those of the medical manipulator 10. The manipulator
808 comprises the working unit 806. The robot arm 802 may comprise
a means for moving the working unit 806, and is not limited to an
installed type, but may be of an autonomous movable type. The
console 804 may comprise a table type, a control panel type, or the
like.
[0122] The robot arm 802 should preferably have six or more
independent joints (rotary shafts, slide shafts, etc.) for setting
the position and orientation of the working unit 806 as desired.
The manipulator 808 is integrally combined with the distal end 810
of the robot arm 802. Instead of the actuator block 30 (see FIG. 1)
described above, the manipulator 808 includes an actuator block
812, which is connected to the distal end 810 and incorporates
motors therein.
[0123] The robot arm 802 operates under the control of the console
804, and may be automatically actuatable according to a program, by
joysticks 814 mounted on the console 804, or by a combination of
the program and the joysticks 814. The console 804 includes therein
the aforementioned functions of the controller 27 (see FIG. 1). The
working unit 806 includes the distal-end working unit 12, as
described above.
[0124] The console 804 includes the two joysticks 814 serving as an
operation command unit, and a monitor 816. Although not shown, the
two joysticks 814 are capable of individually operating two robot
arms 802. The two joysticks 814 are disposed in respective
positions where the joysticks 814 can easily be operated by both
hands of the operator. The monitor 816 displays information such as
an image produced by an endoscope.
[0125] The joysticks 814 can be moved vertically and horizontally,
or twisted and tilted, and the robot arm 802 can be moved depending
on such movements of the joysticks 814. The joysticks 814 may be
master arms. The robot arm 802 and the console 804 may communicate
with other via a communication means comprising a wired link, a
wireless link, a network, or a combination thereof.
[0126] Although a certain preferred embodiment of the present
invention has been shown and described in detail, it should be
understood that various changes and modifications may be made to
the embodiment without departing from the scope of the invention as
defined in the appended claims.
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